Обсуждение: if exists / where exisyts....

i want to test if a table exists before to drop this......

the :
if exists (select 1 from pg_tables where tablename = "thetable")
drop table thetable
;

don't work....

i try :

wher e exists (....)
;

don't work.


but the expresssion :
select * from pg_tables where exists(select 1 from pg_tables where 
tablename = "thetable")
;

work

On Fri, 2002-05-24 at 09:12, Denis Cartier Millon wrote:
> i want to test if a table exists before to drop this......
> 
> the :
> if exists (select 1 from pg_tables where tablename = "thetable")
> drop table thetable
> ;
> 
> don't work....

I'd use the system catalogs:
test2=# select count(*) from pg_class where relname = 'foo';count 
-------    1
(1 row)

test2=# select count(*) from pg_class where relname = 'snaggle';count 
-------    0
(1 row)

You can use it for tables, views, indexes (and maybe other
things).

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